The interlaminar shear strength of a unidirectional fiber-reinforced polymer–matrix composite is a fundamental material property that is a limiting design characteristic. To understand the point of weakening and develop a better composite, a simple analytical model is needed to evaluate the interlaminar shear strength. Based on fracture mechanics using a staggered array of parallel fibers with a hexagonal cross-section, the elastic energies of undamaged and damaged cells are obtained. By comparing these energies, the interlaminar shear strength can be calculated. It is found that the predicted interlaminar shear strength decreases with increasing fiber content in a similar manner as the experimental results. Also, the calculated fracture toughness as per Mode II delamination using the measured interlaminar shear strength and the analytical model is quite accurate when compared with various experimental results. Various factors that affect the shear strength are discussed and investigated through results in the literature.
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